1. Field of the Invention
The present invention pertains to a system and method for transferring an integrated offshore platform deck from a vessel to support piles or other substructure.
2. Background
Various methods have been considered for installing offshore platforms on support piles or other support structure. In certain situations, large shipmounted cranes are preferable for transferring an integrated deck from its support vessel to the substructure. In other situations, it is preferred to utilize a ballastable barge or other vessel which supports the platform deck, moves the deck into position over the substructure and then is ballasted down to lower the deck onto the substructure. Aligning the deck with the support piles of the substructure and transferring the weight of the deck to the substructure is a difficult procedure, particularly when motion of the sea is taken into consideration.
Several methods and systems are described in the prior art, such as U.S. Pat. No. 4,436,454 to Ninet, et al, issued Mar. 13, 1984, which describes a stabbing tip assembly with a centering pin extending below the lower end of the deck leg, and a compressible damping unit interposed between the centering pin and an upper section of the centering mechanism. U.S. Pat. No. 4,607,982, issued to Brasted, et al on Aug. 26, 1986, describes a platform deck to substructure mating system and method wherein a separate locating pin between the deck and the substructure guides the deck leg into position for being supported by a resilient neoprene pad interposed between the deck leg and a sand jack. U.S. Pat. No. 4,729,695 to Sylvestri, issued Mar. 8, 1988, describes a deck to platform transfer system wherein hydraulic lift cylinders are used to raise and then lower the deck legs onto the jacket legs. U.S. Pat. No. 4,761,097 to Turner, issued Aug. 2, 1988, describes a system for absorbing the shock loading between the deck legs and the substructure piles wherein a sand bin is provided on the pile to receive the tip of the deck leg to minimize dynamic forces that occur during the mating procedure. U.S. Pat. No. 4,848,967 to Weiler, issued Jul. 18, 1989, describes a deck to substructure transfer system wherein each of the deck legs includes a hydro-pneumatic cylinder and piston type actuator for stabbing into receptacles on the substructure piles which cylinders work in conjunction with stacked elastomeric disks which are compressed between the cylinders and the deck. U.S. Pat. Nos. 4,242,011 to Karsan, et al, issued Dec. 30, 1980; 4,252,468 and 4,252,469 both issued to Blight on Feb. 24, 1981, describe a method and system for transferring a deck from a barge to a substructure wherein locating pins which align the deck to the substructure are fitted with lateral and vertical force damping hydraulic cylinders. U.S. Pat. No. 4,930,938 to Rawstron, et al describes a deck to substructure mating assembly adapted to accommodate misalignment and fitted with primary and secondary load transfer devices.
Several aspects of the present invention are provided to improve the construction and operation of means for performing the alignment or locating function, the vertical and lateral shock force absorbing function and the final load transfer of the deck to the substructure pile which will enable more efficient and less hazardous, with respect to potential damage to the structures, transfer of an integrated deck or platform to a substructure located offshore.